The storming of the US Capitol by a pro-Trump mob last week has triggered a wave of threats against UK politicians by British far-right activists, many of whom are citing antisemitic conspiracy theories to justify their rage. 

An investigation by communal security organisation CST revealed a number messages posted on Gab and 4Chan — social media platforms popular with the UK far-right — calling for a similar assault on Parliament or Downing Street, with Jews in the firing line as “enablers” of a corrupt establishment.

One user on a network called “Britfam”, a group on the Gab website, wrote: “Be afraid, Boris be very afraid, the people have the real power, not you, you are finished, traitor.”

Another person in the same group posted a picture of the prime minister with the message, “This is what a nervous Yid looks like.”

One Britfam member described a Facebook executive as “another Jew silencing us” after the site banned Donald Trump indefinitely in the wake of last week’s violence.

Another alluded to the Rothschild family, a focus of many antisemitic tropes, as they called on others to “hunt” the “AP”, an apparent reference to the Associated Press, a news agency.

CST said about Britfam, which has nearly 5,000 UK members, that “usually when looking at their reactions to events, there is a lot of general commentary, and a few threats or inciting posts.” But a “significant proportion” of posts responding to the violence were “threats against UK politicians” and calls for similar action in the UK.

Experts on extremism are also warning that some of the conditions that led to the assault on the US Capitol are present in the UK.

Blyth Crawford, a research fellow at the International Centre for the Study of Radicalisation at King’s College London, said: “What is notable about the events in the US is how they were organised largely online and the overarching narrative of persecution which allowed radical right and extreme right groups to unite under a shared sense of a need to ‘fight for justice’.

“The universality of this narrative and the use of social media as an organising space are certainly things that the far right in the UK could capitalise on.” However, she added that it was not possible to predict the exact response in the UK.

Patrik Hermansson, a researcher at the counter-extremism charity Hope Not Hate, said many on the far-right continued to express support for Mr Trump or spread false claims to distance themselves from the riot. 

He said that calls for violent uprisings remained very “marginal” but stressed the seriousness of the threat posed by online extremism.

While it is “too early to tell” whether extremist activity would continue to thrive in a Biden era, he said there was no evidence to suggest it would decrease.

 “What we have been seeing over the last two years is the feeling that Trump was elected and Brexit happened, things are not happening fast enough and that leads to a feeling that the democratic system isn’t working or a disappointment, which legitimises in their eyes more violent action and direct action.”

Ms Crawford, meanwhile, expressed particular concern over the “prevalence and universality of cultural-Marxism conspiracies and strong distrust of traditional media reporting.”

She said veiled antisemitic narratives are widespread online and could be a “vehicle for some users to transition into more open antisemitism.”

The CST’s policy director Dave Rich said he was not surprised by the material the charity discovered. “It fits a pattern we have seen before where there is a spike in violent online postings in the immediate aftermath of real-life events, such as the storming of the Capitol, the killing of George Floyd, or terror attacks,” he said. 

He said he was not aware of any specific plans to stage similar events in the UK but said it was possible to imagine “supportive protests” here if tensions continue to escalate. 

While noting recent efforts by some tech companies to crackdown on extremism, Mr Rich said firms must do more to tackle extremism. “The storming of the Capitol was organised and conducted by an extremist movement that was built, organised, radicalised and motivated on social media. 

“It could not have happened without social media and, while it is welcome that tech companies have finally started to take some responsibility for this, they need to address their role in a much more fundamental way,” he said. 

Lord Mann, the government’s adviser on antisemitism, said the “spectre of Nazism was there for the whole world to see in Washington.”

He also said the UK must target its “organisational and communications structures” here. The government’s online harms bill, expected to be laid in Parliament this year, will set out a new and binding duty of care towards online users, as regulated by Ofcom. 

Online platforms will be required to publish annual reports under the new legislation. Ofcom will have enforcement powers, including ability to issue fines of up to £18 million or 10 per cent of global turnover. 

But the CST said that while the bill contains “a lot of good proposals”, it would benefit from a stronger focus on online hate and extremism.

“It is also important that the proposal to apply weaker obligations to smaller companies does not create a loophole that allows the fringe platforms favoured by extremists, like Gab, 4Chan or BitChute, to continue operating as they have been,” Mr Rich added.